<template>
    <div>
        <p>今日温度{{ num }}</p>
        <p>建议穿{{ msg }}</p>
        <button @click="up">升温</button>
        <button @click="down">降温</button>

    </div>
</template>
<script>
export default {
    data() {
        return {
           num:1,
           msg:"棉袄"
        }
    },
    methods: {
        up(){
        this.num += 5
       },
       down(){
        this.num -= 5
       }
    },
    watch:{
        // 监听的变量(新数据,旧数据){}
        num(newVal,oldVal){
            console.log(newVal,oldVal);
            if(newVal < 10) {
                this.msg ="棉袄"
            }else if(newVal < 25 && newVal > 10){
                this.msg = "半袖"
            }else{
                this.msg = "光腚"
            }
        }
    }
}   
</script>
<style lang="">

</style>